Modified ciliary neurotrophic factors

ABSTRACT

Modified ciliary neurotrophic factors and methods for their production and therapeutic use. Also described is a method of screening for novel therapeutic proteins by determining altered electrophoretic binding properties.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to therapeutic CNTF-related polypeptides useful for the treatment of neurological or other diseases or disorders.

[0002] Ciliary neurotrophic factor (CNTF) is a protein that is required for the survival of embryonic chick ciliary ganglion neurons in vitro (Manthorpe et al.,1980, J. Neurochem. 34:69-75). The ciliary ganglion is anatomically located within the orbital cavity, lying between the lateral rectus and the sheath of the optic nerve; it receives parasympathetic nerve fibers from the oculomotor nerve which innervates the ciliary muscle and sphincter pupillae.

[0003] Over the past decade, a number of biological effects have been ascribed to CNTF in addition to its ability to support the survival of ciliary ganglion neurons. CNTF is believed to induce the differentiation of bipotential glial progenitor cells in the perinatal rat optic nerve and brain (Hughes et al., 1988, Nature 335:70-73). Furthermore, it has been observed to promote the survival of embryonic chick dorsal root ganglion sensory neurons (Skaper and Varon, 1986, Brain Res. 389:39-46). In addition, CNTF supports the survival and differentiation of motor neurons, hippocampal neurons and presympathetic spinal cord neurons [Sendtner, et al., 1990, Nature 345: 440-441; Ip, et al. 1991, J. Neurosci. 11:3124-3134; Blottner, et al. 1989, Neurosci. Lett. 105:316-320].

[0004] It has long been known that innervation of skeletal muscle plays a critical role in the maintenance of muscle structure and function.

[0005] Skeletal muscle has been shown recently to be a target of positive CNTF actions. Specifically, CNTF prevents both the denervation-induced atrophy (decreased wet weight and myofiber cross sectional area) of skeletal muscle and the reduced twitch and tetanic tensions of denervated skeletal muscle (Helgren et al., Cell 76:493-504 (1994)). In this model, human CNTF also produces an adverse effect that is manifested as a retardation of weight gain. This adverse effect has also been observed in clinical trials with rHCNTF for the treatment of ALS. Therefore, simultaneous measurements of muscle weight and animal body weight following denervation could be used as a measure of efficacy and adverse reaction, respectively, in response to treatment with rHCNTF or other compounds. The ratio of the potency values obtained from these measurements is defined as the therapeutic index (T.I.), expressed here as TD₂₅/ED₅₀, so that the higher the value of T.I., the safer the compound at a therapeutic dose.

[0006] CNTF has been cloned and synthesized in bacterial expression systems, as described by Masiakowski, et al., 1991, J. Neurosci. 57:1003-1012 and in International Publication No. WO 91/04316, published on Apr. 4, 1991, which are incorporated by reference in their entirety herein.

[0007] The receptor for CNTF (termed “CNTFRα”) has been cloned, sequenced and expressed [see Davis, et al. (1991) Science 253:59-63]. CNTF and the haemopoetic factor known as leukemia inhibitory factor (LIF) act on neuronal cells via a shared signaling pathway that involves the IL-6 signal transducing component gp130 as well as a second, β-component (know as LIFR β); accordingly, the CNTF/CNTF receptor complex can initiate signal transduction in LIF responsive cells, or other cells which carry the gp130 and LIFRβ components [Ip, et al. (1992) Cell 69:1121-1132].

[0008] In addition to human CNTF, the corresponding rat (Stöckli et al., 1989, Nature 342:920-923), and rabbit (Lin et al., 1989, J. Biol. Chem. 265:8942-8947) genes have been cloned and found to encode a protein of 200 amino acids, which share about 80% sequence identity with the human gene. Both the human and rat recombinant proteins have been expressed at exceptionally high levels (up to 70% of total protein) and purified to near homogeneity.

[0009] Despite their structural and functional similarity, recombinant human and rat CNTF differ in several respects. The biological activity of recombinant rat CNTF in supporting survival and neurite outgrowth from embryonic chick ciliary neurons in culture is four times better than that of recombinant human CNTF [Masiakowski et al., (1991), J. Neurochem. 57:1003-1012]. Further, rat CNTF has a higher affinity for the human CNTF receptor than does human CNTF.

[0010] A surprising difference in the physical properties of human and rat CNTF, which are identical in size, is their different mobility on SDS gels. This difference in behaviour suggests the presence of an unusual structural feature in one of the two molecules that persists even in the denatured state (Masiakowski et al., 1991, id.).

[0011] Mutagenesis by genetic engineering has been used extensively in order to elucidate the structural organization of functional domains of recombinant proteins. Several different approaches have been described in the literature for carrying out deletion or substitution mutagenesis. The most successful appear to be alanine scanning mutagenesis [Cunningham and Wells (1989), Science 244: 1081-1085] and homolog-scanning mutagenesis [Cunningham et al., (1989), Science 243:1330-1336]. These approaches helped identify the receptor binding domains of growth hormone and create hybrid proteins with altered binding properties to their cognate receptors.

[0012] To better understand the physical, biochemical and pharmacological properties of rHCNTF, applicant undertook rational mutagenesis of the human and rat CNTF genes based on the different biological and physical properties of their corresponding recombinant proteins (See Masiakowski, P., et al. (1991) J. Neurochem., 57, 1003-1012). Applicant has found that the nature of the amino acid at position 63 could greatly enhance the affinity of human CNTF for sCNTFRα and its biological potency in vitro (Panayotatos, N., et al., J. Biol. Chem., 268, 19,000-19,003 (1993); Panayotatos, N., et al., Biochemistry, 33, 5813-5818 (1994).

SUMMARY OF THE INVENTION

[0013] An object of the present invention is to provide novel CTNF-related neurotrophic factors for the treatment of diseases or disorders including, but not limited to, motor neuron diseases and muscle degenerative diseases.

[0014] A further object of the present invention is to provide a method for identifying CNTF-related factors, other than those specifically described herein, that have improved therapeutic properties.

[0015] These and other objects are achieved in accordance with the invention, whereby amino acid substitutions in human CNTF protein enhance its therapeutic properties. In one embodiment, alterations in electrophoretic mobility are used to initially screen potentially useful modified CNTF proteins.

[0016] In a preferred embodiment, the amino acid glutamine in position 63 of human CNTF is replaced with arginine (referred to as 63QR) or another amino acid which results in a modified CNTF molecule with improved biological activity. In further embodiments, rHCNTF variants combine the 63QR mutation with three other novel features:

[0017] 1) Deletion of the last 13 amino acid residues (referred to as ΔC13) to confer greater solubility to rHCNTF without impairing its activity;

[0018] 2) Substitution of the unique cysteine residue at position 17, which results in stabilization of rHCNTF in physiological buffer, at physiological pH and temperature conditions without affecting its activity; or

[0019] 3) Substitution of amino acid residue 64W, which alters the biological activity of rHCNTF in vitro and which results in a 7-fold improvement of its therapeutic index in vivo.

[0020] In another preferred embodiment, a molecule designated RG297 (rHCNTF,17CA63QRΔC13) combines a 63QR substitution (which confers greater biological potency) with a deletion of the terminal 13 amino acid residues (which confers greater solubility under physiological conditions) and a 17CA substitution (which confers stability, particularly under physiological conditions at 37° C.) and shows a 2-3 fold better therapeutic index than rHCNTF in an animal model.

[0021] In another preferred embodiment, a molecule designated RG242 is described that carries the double substitution 63QR64WA which results in a different spectrum of biological potency and a 7-fold higher therapeutic index.

[0022] In another preferred embodiment, a molecule designated RG290 is described that carries the double substitution 63QRΔC13 which confers greater solubility under physiological conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1—Alignment of CNTF protein sequences. A. Human, rat, rabbit mouse and chicken (Leung, et al., 1992, Neuron 8:1045-1053) sequences. Dots indicate residues found in the human sequence. Panel B. Modified CNTF molecules showing human CNTF amino acid residues (dots) and rat CNTF (residues shown). The name of the purified recombinant protein corresponding to each sequence is shown on the left.

[0024]FIG. 2—Mobility of human, rat and several modified CNTF molecules on reducing SDS-15% polyacrylamide gels. Purified recombinant proteins were loaded as indicated. Markers of the indicated MW were loaded on lane M.

[0025]FIG. 3—Biological activity of two modified CNTF molecules. A. human CNTF (filled diamonds), rat CNTF (open squares), and RPN219 (filled squares). B. human CNTF (filled diamonds), rat CNTF (open squares), and RPN228 (filled squares). Dose response of dissociated E8 chick ciliary neurons surviving at the indicated protein concentration, as a percentage of the number of neurons surviving in the presence of 2 ng/ml rat CNTF. Each experimental point represents the mean of three determinations.

[0026]FIG. 4—Competitive ligand binding towards A.) SCG neurons and B.) MG87/huCNTFR fibroblasts. Standard deviation from the mean of three determinations is shown by vertical bars.

[0027]FIG. 5—Mobility of human and several modified CNTF molecules on SDS-15% polyacrylamide gels. Supernatant (A) and pellet (B) preparations of recombinant human CNTF (designated HCNTF) and several modified CNTF proteins were loaded as indicated. The modified proteins shown are ΔC13 (also known as RG160); 17CA,ΔC13 (RG162); ΔC13,63QR (RG290); and 17CA,ΔC13,63QR (RG297). Markers of the indicated MW were loaded on lane M. Incubation in physiological buffer at 37° C. for 0, 2, 7 and 14 days is indicated in lanes 1-4, respectively.

[0028]FIG. 6—Survival of primary dissociated E8 chick ciliary neurons in response to increasing concentrations of various CNTF variants. Control concentration response curves for rat CNTF and rHCNTF obtained with standard, untreated stock solutions, as well as with four rHCNTF variants, RG297, RG290, RG160 and RG162.

[0029]FIG. 7—Survival of primary dissociated E8 chick ciliary neurons in response to increasing concentrations of various CNTF variants. Control concentration response curves for rat CNTF and rHCNTF obtained with standard, untreated stock solutions, as well as with rHCNTF variant RG228 (also known as RPN228 and having the mutation 63QR).

[0030]FIG. 8—Survival of primary dissociated E8 chick ciliary neurons in response to increasing concentrations of various CNTF variants. Control concentration response curves for rat CNTF and rHCNTF obtained with standard, untreated stock solutions, as well as with rHCNTF variant RG242 (which has the mutation 63QR,64WA).

[0031]FIG. 9—Average plasma concentration time profiles in the rat after intravenous (IV) administration of rHCNTF, RG228 and RG242 normalized to 100 μg/kg dose for all three compounds.

[0032]FIG. 10—Average plasma concentration time profiles in the rat after subcutaneous (SC) administration of rHCNTF, RG228 and RG242 normalized to 200 μg/kg dose for all three compounds.

[0033]FIG. 11—Comparison of dose dependent rescue of rat muscle wet weight of (A) hCNTF vs. RG228; (B) hCNTF vs. RG297 and (C) hCNTF vs. RG242.

[0034]FIG. 12—Comparison of in vivo toxicity for hCNTF, RG228, RG242 and RG297.

DETAILED DESCRIPTION OF THE INVENTION

[0035] The present invention relates to a method of treating neurological diseases and disorders in humans or animals. It is based, in part, on the initial finding that recombinant rat CNTF binds more efficiently to the human CNTF receptor than does recombinant human CNTF and the subsequent discovery that amino acid substitutions which cause human CNTF to more closely resemble rat CNTF result in enhanced binding of the modified CNTF to the human CNTF receptor and concomitant enhanced biological activity.

[0036] In a preferred embodiment, alteration of a single amino acid of the human CNTF protein results in a significant enhancement of the ability of the protein to promote the survival and outgrowth of ciliary ganglion neurons.

[0037] Recombinant human and rat CNTF have the same number of amino acids (199) and similar mass (MW 22,798 and 22,721 respectively, after removal of the N-terminal methionine). Yet, on reducing SDS-PAGE gels, recombinant human CNTF migrates as a protein of MW=27,500, whereas rat CNTF migrates with the expected mobility. In addition, human CNTF has four times lower biological activity towards chick ciliary ganglion (CG) neurons than rat CNTF and the human protein competes for binding to the human or the rat receptor on cell surfaces much less effectively than rat CNTF.

[0038] The above observation led to a directed effort to identify the region on the CNTF molecule responsible for these differences. This method involved the exchange, by genetic engineering methods, of parts of the human CNTF sequence with the corresponding rat CNTF sequence and vice versa. To achieve this, advantage was taken of restriction sites that are common to the two CNTF genes and unique in their corresponding expression vectors. When necessary, such sites were engineered in one or the other of the two genes in areas that encode the same protein sequence. With this approach, expression vectors were obtained for each of the modified proteins shown in FIG. 1. After isolating the individual proteins to at least 60% purity, their properties, as compared to those of human and rat CNTF were determined.

[0039] Because the electrophoretic mobilities of human and rat CNTF differ significantly, the effect of each amino acid substitution was monitored initially by making a determination of the effect of such change on the mobility of the protein. As described herein, electrophoretic mobility data indicated that all of the modified human CNTF molecules that migrated to the same position as rat CNTF had the single amino acid substitution Gln63→Arg (063→R).

[0040] Modified human CNTF proteins that demonstrated an electrophoretic mobility similar to that of the rat CNTF molecule were subsequently examined for biological activity and receptor binding.

[0041] CNTF is characterized by its capacity to support the survival of dissociated ciliary neurons of E8 chick embryos. By this criterion, purified recombinant rat CNTF is as active as the native protein from rat, but four times more active than recombinant human CNTF [Masiokowski, et al. (1991), id]. The same assay was utilized to determine the biological activity of the altered molecules prepared as described above. As described herein, all of the modified CNTF molecules that had the Q63→R substitution exhibited an increased ability to support the survival of ciliary ganglion neurons as compared to the parent human CNTF protein. Such results indicated a strong correlation between alteration of the electrophoretic mobility and enhanced biological properties.

[0042] In addition to measuring the biological effect of modifications made to human CNTF, an indication of the potential biological activity of each of the molecules may also be obtained by determining the effect of each modification on the ability of the molecules to bind to the CNTF receptor.

[0043] In one embodiment, the ability of the modified human CNTF proteins to compete with rat CNTF for binding to rat superior cervical ganglia neurons (SCGs) is measured. As described herein, human CNTF is about 90 times less potent in displacing ¹²⁵I-labelled rat CNTF binding from these cells than unlabelled rat CNTF. Several of the modified human CNTF proteins described herein, however, are more potent than the human CNTF in displacing the rat protein. All of the molecules described herein that had such increased competitive binding ability were molecules that exhibited altered electrophoretic mobility, wherein the molecules migrated in a manner similar to rat CNTF.

[0044] In another embodiment, cells, such as MG87 fibroblasts, are engineered to express the human CNTF receptor α-component and such cells are used to assay the binding capability of the modified protein to the human receptor. Human CNTF is about 12 times less potent than rat CNTF in competing with ¹²⁵I-labelled rat CNTF for binding to the human CNTF receptor. Several of the modified human CNTF molecules described herein, including all of those with electrophoretic mobility that resemble rat rather than human CNTF, were more potent than human CNTF in competing with binding of ¹²⁵I-rat CNTF to the cells expressing the human CNTF receptor.

[0045] In another embodiment, an animal model with demonstrated utility in providing an indication of the ability of certain growth and other factors to prevent degeneration of retinal photoreceptors may be used to assess the therapeutic properties of the modified CNTF molecules according to the present invention. As described in Example 4, hCNTF (Gln63→Arg) has a ten-fold higher ability than recombinant human CNTF to prevent degeneration of photoreceptors in a light-induced damage model of retinal degeneration.

[0046] Thus, according to the invention, certain amino acid substitutions in the human CNTF protein result in modified human CNTF proteins that exhibit enhanced binding to the human CNTF receptor and therefore, would be expected to have enhanced therapeutic properties.

[0047] The modified CNTF molecules useful for practicing the present invention may be prepared by cloning and expression in a prokaryotic or eukaryotic expression system. The recombinant neurotrophin gene may be expressed and purified utilizing any number of methods. The gene encoding the factor may be subcloned into a bacterial expression vector, such as for example, but not by way of limitation, pCP110.

[0048] The recombinant factors may be purified by any technique which allows for the subsequent formation of a stable, biologically active protein. For example, and not by way of limitation, the factors may be recovered from cells either as soluble proteins or as inclusion bodies, from which they may be extracted quantitatively by 8M guanidinium hydrochloride and dialysis. In order to further purify the factors, conventional ion exchange chromatography, hydrophobic interaction chromatography, reverse phase chromatography or gel filtration may be used.

[0049] According to the present invention, modified CNTF molecules produced as described herein, or a hybrid or mutant thereof, may be used to promote differentiation, proliferation or survival in vitro or in vivo of cells that are responsive to CNTF, including cells that express receptors of the CNTF/IL-6/LIF receptor family, or any cells that express the appropriate signal transducing component, as described, for example, in Davis, et al. (1992) Cell 69:1121-1132. Mutants or hybrids may alternatively antagonize cell differentiation or survival.

[0050] The present invention may be used to treat disorders of any cell responsive to CNTF or the CNTF/CNTF receptor complex. In preferred embodiments of the invention, disorders of cells that express members of the CNTF/IL-6/LIF receptor family may be treated according to these methods. Examples of such disorders include but are not limited to those involving the following cells: leukemia cells, hematopoietic stem cells, megakaryocytes and their progenitors, DA1 cells, osteoclasts, osteoblasts, hepatocytes, adipocytes, kidney epithelial cells, embryonic stem cells, renal mesangial cells, T cells, B cells, etc.

[0051] Accordingly, the present invention provides for methods in which a patient suffering from a CNTF-related neurological or differentiation disorder or disease or nerve damage is treated with an effective amount of the modified CNTF, or a hybrid or mutant thereof. The modified CNTF molecules may be utilized to treat disorders or diseases as described for CNTF in International Publication No. WO91/04316 published on Apr. 4, 1991 by Masiakowski, et al. and for CNTF/CNTFR complex as described in International Publication No. WO91/19009 published on Dec. 12, 1991 by Davis, et al. both of which are incorporated by reference in their entirety herein.

[0052] Such diseases or disorders include degenerative diseases, such as retinal degenerations, diseases or disorders involving the spinal cord, cholinergic neurons, hippocampal neurons or diseases or disorders involving motorneurons, such as amyotrophic lateral sclerosis or those of the facial nerve, such as Bell's palsy. Other diseases or disorders that may be treated include peripheral neuropathy, Alzheimer's disease, Parkinson's disease, Huntington's chorea, or muscle atrophy resulting from, for example, denervation, chronic disuse, metabolic stress, and nutritional insufficiency or from a condition such as muscular dystrophy syndrome, congenital myopathy, inflammatory disease of muscle, toxic myopathy, nerve trauma, peripheral neuropathy, drug or toxin-induced damage, or motor neuronopathy.

[0053] The present invention also contemplates diseases or disorders resulting from damage to the nervous system, wherein such damage may be caused by trauma, surgery, infarction, infection and malignancy or by exposure to a toxic agent.

[0054] The present invention also provides for pharmaceutical compositions comprising a modified CNTF molecule or hybrid or mutant thereof, as described herein, as the sole therapeutic agent or in a complex with the CNTF receptor, in a suitable pharmacologic carrier.

[0055] The active ingredient, which may comprise the modified CNTF, stable modified CNTF/CNTF receptor complex, or a hybrid or mutant thereof, should be formulated in a suitable pharmaceutical carrier for systemic or local administration in vivo by any appropriate route including, but not limited to injection (e.g., intravenous, intraperitoneal, intramuscular, subcutaneous, endoneural, perineural, intraspinal, intraventricular, intravitreal, intrathecal etc.), by absorption through epithelial or mucocutaneous linings (e.g., oral mucosa, rectal and intestinal mucosa, etc.); or by a sustained release implant, including a cellular or tissue implant.

[0056] Depending upon the mode of administration, the active ingredient may be formulated in a liquid carrier such as saline, incorporated into liposomes, microcapsules, polymer or wax-based and controlled release preparations, or formulated into tablet, pill or capsule forms.

[0057] The concentration of the active ingredient used in the formulation will depend upon the effective dose required and the mode of administration used. The dose used should be sufficient to achieve circulating plasma concentrations of active ingredient that are efficacious. Effective doses may be extrapolated from dose-response curves derived from in vitro or animal model test systems.

[0058] As described herein, applicants have determined that altered electrophoretic mobility provides a reliable method for screening for proteins with enhanced biological activity or ligand binding capability. Accordingly, the method described herein may have general applicability in screening for novel therapeutic proteins. Such a method would involve determining the electrophoretic mobility of a wild-type human protein, introducing amino acid substitutions into the wild-type human protein and identifying as potential candidates substituted proteins that have altered electrophoretic mobility as compared to the electrophoretic mobility of the wild-type protein. Such substitute proteins could be further tested to determine their biological activity and/or binding affinity. Potential amino acid substitutions could be based, for example, on comparable sequences from homologous proteins of non-human species.

[0059] One skilled in the art will recognize that other alterations in the amino acid sequence of CNTF may provide enhanced properties to the molecule. One skilled in the art will also recognize that CNTF homologues from other species, i.e. mouse, rabbit and chicken, may also have enhanced properties in treating human diseases or disorders. Thus, the present invention contemplates a method of identifying novel neurotrophic factors, whereby neurotrophic factors from species other than human are identified and assayed with respect to their ability to bind the human receptor as well as their biological activity in human cell lines and in vivo systems. When neurotrophic factors from animal species are identified which have novel properties, methods known to those in the art, such as those described herein, can be used to interchange portions of the human factor with the animal-derived factor to create novel neurotrophic factors with enhanced therapeutic properties. Here we compare the therapeutic index of rHCNTF derivatives with the 63QR mutation and/or in combination with other structural modifications of rHCNTF.

[0060] The solubility of recombinant human CNTF (rHCNTF) is very limited in physiological buffer, e.g., Phosphate-Buffered-Saline, pH 7.4 (PBS). Furthermore, the solubility over at least the 4.5-8.0 pH range depends strongly on the temperature and on the time of incubation. At 5° C., the solubility of rHCNTF in PBS is 1 mg/ml and the solution is stable for a few hours, but at 37° C. its solubility is only 0.1 mg/ml after 2 hr and 0.05 mg/ml after 48 hrs. This limited solubility and thermal stability preclude stable formulation of rHCNTF in physiological buffer. Such formulations are particularly desirable for continuous administration through the cerebrospinal fluid (CSF).

[0061] It was discovered that rHCNTF lacking the last 13 amino acid residues from the carboxyl end (rHCNTF,ΔC13 also designated RPN160 or RG160) retains full biological activity and is soluble at low temperatures (5-10° C.) to at least 12 mg/ml. Yet, despite this far greater solubility, rHCNTF,ΔC13 still falls out of a PBS solution upon incubation at 37° C. over a period of several hours, even at concentrations as low as 0.1 mg/ml.

[0062] It was determined that the thermal instability of rHCNTF and rHCNTF,ΔC13 was the result of aggregation that was initiated by intermolecular disulfide bond formation and depended strongly on protein concentration and temperature. By replacing the single cysteine residue at position 17 of human CNTF with an alanine residue, proteins were obtained that show far greater stability and maintain their biological activity after incubation for at least 7 days in PBS at 37° C. This property is maintained in rHCNTF,63QR variants which have higher potency due to the substitution of the glutamine residue at position 63 by arginine. In a particular example, rHCNTF,17CA,63QR,ΔC13 (also designated RG297) shows greater biological potency than rHCNTF because of the 63QR substitution, greater solubility because of the ΔC13 deletion and greater stability because of the 17CA substitution.

EXAMPLES Example 1 Electrophoretic Mobility of Modified Human CNTF Molecules

[0063] Materials and Methods

[0064] Preparation of Modified CNTF Molecules

[0065] Bacterial Strains and Plasmids

[0066]E. coli K-12 RFJ26 is a strain that overproduces the lactose operon repressor.

[0067] The expression vectors pRPN33, which carries the human CNTF gene and pRPN110 which carries the rat CNTF gene are nearly identical (Masiakowski, et al. 1991, id.).

[0068] Plasmid pRPN219 was constructed by first digesting pRPN33 with the restriction enzymes Nhe1 plus Hind3 and gel purifying the 4,081 bp fragment. The second, much smaller fragment which codes for part of the human CNTF gene was subsequently replaced with an 167 bp Nhe1-Hind3 fragment that was obtained by PCR amplification from the rat gene using the primers RAT-III-dniH: 5′ ACGGTAAGCT

[0069] TGGAGGTTCTC 3′; and RAT-Nhe-I-M: 5′ TCTATCTGGC TAGCAAGGAA GATTCGTTCA GACCTGACTG CTCTTACG 3′.

[0070] Plasmid pRPN228 was constructed in the same manner as pRPN219, except that the 167 bp replacement fragment was amplified using the DNA primers Rat-III-dniH-L-R : 5′ AAG GTA CGA TAA GCT TGG AGG TTC TCT TGG AGT CGC TCT GCC TCA GTC AGC TCA CTC CAA CGA TCA GTG 3′ and Rat-Nhe-I: 5′ TCT ATC TGG CTA GCA AGG AAG 3′.

[0071] Plasmids pRPN186, pRPN187, pRPN188, pRPN189, pRPN192, pRPN218, and pRPN222 were generated by similar means or by direct exchange of DNA fragments using the unique restriction sites shown in FIG. 1.

[0072] The identity of all plasmids was confirmed by restriction analysis and DNA sequencing.

[0073] Protein Purification

[0074] Induction of protein synthesis, selective extraction, solubilization and purification from inclusion bodies were as described for rat and human CNTF (Masiakowski, et al. 1991, id.) except that gel filtration was occasionally used instead or in addition to ion exchange chromatography. Alternatively, proteins were purified from the supernatants of cell lysates by streptomycin and ammonium sulfate fractionation, followed by column chromatography, as described for other proteins (Panayotatos et al., 1989, J. Biol. Chem. 264:15066-15069). All proteins were isolated to at least 60% purity.

[0075] Conditions for enzymatic reactions, DNA electrophoresis and other techniques used in these studies have been described in detail (Panayotatos, N. 1987, Engineering an Efficient Expression System in Plasmids: A practical Approach (Hardy, K. G. ed.) pp 163-176, IRL Press, Oxford, U. K.).

[0076] Results

[0077] The mobilities of human, rat and several chimeric CNTF molecules on reducing SDS-polyacrylamide gels are shown in FIG. 2. The chimeric molecules RPN186, RPN189, RPN218 and RPN228 exhibit mobilities comparable to rat CNTF, whereas RPN187, RPN188, RPN192 and RPN222 exhibit mobilities comparable to human CNTF. Cross-reference of these results to the aligned sequences of these proteins in FIG. 1 reveals that all proteins carrying an arginine residue at position 63 (R63) display the mobility of rat CNTF. In the case of RPN228, this single amino acid substitution (Q63→R) is sufficient to confer to human CNTF the normal mobility of rat CNTF.

[0078]FIG. 2 also provides a measure of the purity of the different recombinant proteins. By visual inspection, purity varies from 60% for RPN189 to better than 90% for RPN228.

Example 2 Measurement of Binding Activity of Modified CNTF Molecules

[0079] Materials and Methods

[0080] Preparation of ²⁵¹I-CNTF

[0081] Recombinant rat CNTF (28 μg) in 37 μl 0.2 M sodium borate buffer, pH 8.5 was transfered to a vial containing 4 mCi, (2,000 Ci/mmole; NEN) of 1251 and reagent (Bolton and Hunter,1973, Biochem J. 133: 529-539) which had been dried under a gentle stream of nitrogen. Reactions were incubated for 45 min at 0° C. followed by 15 min at room temperature and terminated by the addition of 30 ml of 0.2 M glycine solution. After 15 min, 0.2 ml PBS containing 0.08% gelatin was also added and the mixture was passed through a Superdex-75 column (Pharmacia) to separate the labelled monomeric CNTF from dimeric and other multimeric derivatives. Percentage of incorporation was typically 20%, as determined by thin layer chromatography and the specific activity was typically around 1,000 Ci/mmole. The monomeric ¹²⁵I-CNTF was stored at 4° C. and used up to one week after preparation. As a test of structural and conformational integrity, ¹²⁵I-CNTF (approximately 10,000 cpm) was mixed with a 5 μg unlabelled CNTF and analyzed by native gel electrophoresis. One major band was visible by either Coomassie staining or autoradiography. ¹²⁵I-CNTF also showed comparable activity to native CNTF in supporting survival of E8 chick ciliary neurons in culture.

[0082] Tissue Culture Techniques

[0083] Superior cervical ganglia (SCG) from neonatal rats were treated with trypsin (0.1%), mechanically dissociated and plated on a poly-ornithine (30 μg/ml) substratum. Growth medium consisted of Ham's nutrient mixture F12 with 10% heat-inactivated fetal bovine serum (Hyclone), nerve growth factor (NGF) (100 ng/ml), penicillin (50 U/ml) and streptomycin (50 μg/ml). Cultures were maintained at 37° C. in a humidified 95% air/5% CO₂ atmosphere. Ganglion non-neuronal cells were eliminated by treatment with araC (10 μM) on days 1 and 3 of culture. Cultures were fed 3 times/week and were routinely used for binding assays within 2 weeks.

[0084] MG87/CNTFR is a fibroblast cell line transfected with the human CNTFα receptor gene (Squinto, et al.,1990, Neuron 5:757-766; Davis et al., 1991, Science 253:59-63).

[0085] Binding Assays

[0086] Binding was performed directly on cell monolayers. Cells in culture wells were washed once with assay buffer consisting of phosphate buffered saline (PBS; pH 7.4), 0.1 mM bacitracin, 1 mM PMSF, 1 μg/ml leupeptin, and 1 mg/ml BSA. After incubation with ¹²⁵I-CNTF for 2 hours at room temperature, cells were quickly washed twice with assay buffer, lysed with PBS containing 1% SDS and counted in a Packard Gamma Counter. Non-specific binding was determined in the presence of 1,000-fold excess of unlabelled CNTF. Specific binding towards MG87/CNTFR was 80-90%. Data were analyzed using the GRAPHPAD program (ISI, Philadelphia, Pa.).

[0087] Results

[0088] Competition curves of purified recombinant human, rat and CNTF RPN219 towards ¹²⁵I-rat CNTF for binding on rat SCG neurons are shown in FIG. 4a. Both rat and human CNTF compete with ¹²⁵I-rat CNTF for binding to SCG neurons, but human CNTF (IC50=25 nM) is 90 times less potent in displacing 125I-rat CNTF binding than unlabelled rat CNTF (IC50=0.28 nM). In contrast, RPN219 is almost as potent as rat CNTF and clearly more potent than human CNTF (IC50=0.3 nM).

[0089] Similar results were obtained from competition experiments with mouse fibroblasts transfected with a plasmid directing the expression of the human CNTF receptor (FIG. 4b). Both rat, human and RPN228 compete with ¹²⁵I-rat CNTF for binding to MG87/CNTFR cells. Human CNTF (IC50=30 nM) is 12 times less potent than rat CNTF (IC50=2.8 nM), whereas RPN228 is clearly more potent than the human protein (IC50=5.6 nM).

[0090] Competition binding experiments with the other modified CNTF proteins shown in FIG. 1 also demonstrated that proteins having R63 displayed the biological activity of rat CNTF, whereas proteins having Q63 displayed the binding properties of human CNTF (data not shown). These results indicate that the single amino acid substitution (Q63→R) is sufficient to confer to human CNTF the receptor binding properties characteristic of rat CNTF.

Example 3 Measurement of Biological Activity of Modified CNTF Molecules

[0091] Materials and Methods

[0092] Recombinant CNTF was assayed on dissociated cultures of chick ciliary ganglion (CG) neurons as described (Masiakowski et al. 1991, id.), except that surviving cells were stained with MTT (Mosmann, T. 1983; J. Immunol. Methods 65:55-63).

[0093] Results

[0094]FIG. 3 shows dose-response curves of dissociated, neuron-enriched cultures of E8 chick embryo ciliary ganglia for purified recombinant human, rat and the modified CNTF proteins RPN219 and RPN228. By this assay, the biological activity of the chimeric proteins is indistinguishable from that of purified recombinant rat CNTF and clearly higher than that of recombinant human CNTF. Comparison of the dose-response curves in FIG. 3 also shows that the maximal levels of surviving neurons obtained with RPN219, RPN228 or rat CNTF are higher than those obtained with human CNTF. These results suggest that RPN219 and RPN228, like rat CNTF, are active towards a larger population of neurons than human CNTF. In parallel experiments, the biological activity of the other modified CNTF proteins shown in FIG. 1 was examined. In every case, modified CNTF proteins carrying the (Q63→R) substitution displayed the biological activity of rat CNTF whereas proteins having Q63 displayed the activity of human CNTF (data not shown).

[0095] Overall, these results indicate that the single amino acid substitution (Q63→R) is sufficient to confer to human CNTF the biological activity of rat CNTF.

Example 4 Use of Modified CNTF To Prevent Light Induced Photoreceptor Injury

[0096] Albino rats of either the F344 or Sprague-Dawley strain were used at 2-5 months of age. The rats were maintained in a cyclic light environment (12 hr on: 12 hr off at an in-cage illuminance of less than 25 ft-c) for 9 or more days before being exposed to constant light. The rats were exposed to 1 or 2 weeks of constant light at an illuminance level of 115-200 ft-c (most rats received 125-170 ft-c) provided by two 40 watt General Electric “cool-white” fluorescent bulbs with a white reflector that was suspended 60 cm above the floor of the cage. During light exposure, rats were maintained in transparent polycarbonate cages with stainless steel wire-bar covers.

[0097] Two days before constant light exposure, rats anesthetized with a ketamine-xylazine mixture were injected intravitreally with 1 μl of rat CNTF, human CNTF or modified CNTF [hCNTF (Q63→R)] dissolved in phosphate buffered saline (PBS) at a concentration of 0.1 to 500 ng/μl. The injections were made with the insertion of a 32 gauge needle through the sclera, choroid and retina approximately midway between the ora serrata and equator of the eye. In all cases, the injections were made into the superior hemisphere of the eye.

[0098] Immediately following constant light exposure, the rats were sacrificed by overdose of carbon dioxide followed immediately by vascular perfusion of mixed aldehydes. The eyes were embedded in epoxy resin for sectioning at 1 μm thickness to provide sections of the entire retina along the vertical meridian of the eye. The degree of light-induced retinal degeneration was quantified by assessing the degree of photoreceptor rescue by a 0-4+ pathologist's scale of rescue, 4+ being maximal rescue and almost normal retinal integrity. The degree of photoreceptor rescue in each section, as based on comparison to the control eye in the same rat, was scored by four individuals. This method has the advantage of considering not only the ONL thickness, but also more subtle degenerative changes to the photoreceptor inner and outer segments, as well as spatial degenerative gradients within the eye. Three eyes were examined for each time point to generate a dose response curve.

[0099] Results

[0100] The degree of rescue was measured for human, rat and hCNTF (Q63→R). The data indicated that both rat and hCNTF (Q63→R) had ten-fold greater ability to rescue photoreceptors in the light damage model than did recombinant human CNTF.

[0101] It is to be understood that while the invention has been described above in conjunction with preferred specific embodiments, the description and examples are intended to illustrate and not limit the scope of the invention, which is defined by the scope of the appended claims.

Example 5

[0102] Materials and Methods

[0103] Recombinant human CNTF variants were genetically engineered, expressed in E. coli and recovered at greater than 90% purity, as described previously (Masiakowski et al., 1991; Panayotatos et al., 1993).

[0104] The following stock solutions were prepared freshly in PBS at 5° C.: rHCNTF 0.5 mg/ml RG160 (rHCNTF, ΔC13) 0.5 mg/ml RG162 (rHCNTF, 17CA, ΔC13) 0.5 mg/ml RG290 (rHCNTF, 63QR, ΔC13) 1.2 mg/ml RG297 (rHCNTF, 17CA, 63QR, ΔC13) 0.4 mg/ml

[0105] To determine the stability of rHCNTF and several derivatives in physiological buffer at 37° C., stock solutions were dialyzed exhaustively against PBS at 5° C., diluted with PBS to 0.1 mg/ml and sterilized by filtration. Aliquots (0.2 ml), were transfered into 0.5 ml capacity polypropylene centrifugation tubes. The tubes were placed in a 37° C. incubator and, at the indicated times, individual tubes were removed and centrifuged at 15,000 rpm for 3 min at room temperature to separate soluble protein from insoluble precipitates. Supernatants were pipetted off into clean tubes containing an equal volume of 2× protein gel sample buffer, placed in a 85° C. bath for 2 min, mixed and stored at −20° C. until analysis by 15% SDS-PAGE. Pellets were resuspended in 1/10 original volume of water, mixed with an equal volume of 2× protein gel sample buffer and treated as above.

[0106] Methods for biological activity assays on E8 chick ciliary neurons and for protein gel electrophoresis have been described (Masiakowski et al., 1991; Panayotatos et al., 1993). Protein gel sample buffer (2×) consists of 12.5 ml TrisHCl, pH 6.8-20 ml glycerol—40 ml 10% SDS and 5 mg Bromophenol Blue per 100 ml.

[0107] Results

[0108] The solubility of rHCNTF is particularly limited in physiological buffer at neutral pH. Furthermore, the solubility over a broad pH range (4.5-8.0) depends strongly on the temperature and on the time of incubation. At 5° C., the solubility of rHCNTF in PBS is 1.4 mg/ml and the protein remains in solution for a few hours. In sharp contrast to the limited solubility of rHCNTF, the variant rHCNTF,ΔC13 can be concentrated to at least 12 mg/ml at 5° C. Despite this greater solubility, however, rHCNTF,ΔC13 still shows strong instability in physiological buffer, pH and temperature conditions. Upon incubation at 37° C., rHCNTF,ΔC13 falls out of solution at a rate that depends on the initial concentration.

[0109] To determine the cause of this instability, we analyzed the physical integrity of rHCNTF and several variants in parallel experiments. FIG. 5 shows that incubation of rHCNTF in physiological buffer at 37° C. for 0, 2, 7 and 14 days (lanes 1-4, respectively) caused progressive disappearance of the protein from the supernatants, accompanied by concomitant progressive appearance in the pellets. Furthermore, a good proportion of rHCNTF in the pellets appeared as a 48 kD species that corresponded to the size of dimeric rHCNTF (FIG. 5, double arrow). At longer incubation times, a small proportion of higher order aggregates was also evident. However, when the same samples were analyzed on the same type of gel but in the presence of disulfide reducing agents, the 48 kD species was converted to monomeric rHCNTF, evidence that the 48 kD species represents rHCNTF dimers covalently linked by disulfide bonds. Such dimers would be expected to form through the unique cysteine residue of rHCNTF. Therefore, these results indicated that the instability of rHCNTF at 37° C. is caused by aggregation initiated by intermolecular disulfide bond formation.

[0110] Similar results were obtained with two rHCNTF variants, rHCNTF,ΔC13 and rHCNTF,63QR,ΔC13, except that the appearance of insoluble aggregates in the pellets was somehow slower in the case of rHCNTF,ΔC13 (FIG. 5). Given the fact that the ΔC13 deletion confers to rHCNTF much greater solubility in physiological buffer, the improved stability of rHCNTF,ΔC13 is most likely an indirect consequence of its greater solubility.

[0111] To further test the possibility that the instability of rHCNTF at 37° C. is caused by aggregation initiated by intermolecular disulfide bond formation, the unique cysteine residue at position 17 was substituted by alanine, using established genetic engineering methodology. The two rHCNTF variants, rHCNTF,17CA,ΔC13 and rHCNTF,17CA,63QR,ΔC13 generated by this process were subjected to the same analysis by non-reducing 15% SDS-PAGE. FIG. 5 shows that even after incubation for 14 days at 37° C. both proteins remained soluble with no evidence of dimerization or aggregate formation. Even in the small proportion of protein found in the pellets, which represented mostly the small amount of soluble protein remaining in the centrifuge tubes after removal of the supernatant, there was little evidence of dimerization. These results confirmed the conclusion that the instability of rHCNTF is caused by aggregation initiated by intermolecular disulfide bond formation, and demonstrated that elimination of the free —SH functional group in other rHCNTF variants, e.g. RG297, also result in greater stability.

[0112] To test whether the proteins remaining in solution after incubation at 37° C. were still biologically active, samples were analyzed for neuronal survival activity. FIG. 6 shows control concentration response curves for rat CNTF and rHCNTF obtained with standard, untreated stock solutions, as well as with four rHCNTF variants incubated for 7 days at 37° C. Of the latter, the proteins carrying the 17CA mutation, RG297 and RG162, were assayed at their nominal concentrations, whereas RG290 and RG160 were assayed after correcting their concentrations for the amount of protein remaining in solution. FIG. 6 shows that the concentration response curves displayed by these compounds are those expected from these proteins in their fully active form: RG160 and RG162 show the same potency as rHCNTF within experimental error, whereas RG290 and RG297 that carry the 63QR substitution show 4-5 fold higher potency than rHCNTF, as previously observed (Panayotatos, N., et al., (1993)) and as shown in FIG. 7. Therefore, incubation of rHCNTF and its derivatives at 37° C. for 7 days does not cause loss of biological activity, only loss of protein through dimerization followed by precipitation.

Example 6

[0113] Materials and Methods

[0114] Protein Engineering and Purification—The following rHCNTF variants were compared to rHCNTF:

[0115] RG228 (rHCNTF,63QR);

[0116] RG297 (rHCNTF,17CA,63QR,ΔC13)

[0117] RG242 (rHCNTF,63QR64WA)

[0118] These proteins were genetically engineered, expressed in E. coli and recovered at greater than 90% purity by the methodology described for rHCNTF (Masiakowski et al., 1991; Panayotatos et al., 1993).

[0119] Biological Activity Assays—Methods for biological activity assays on E8 chick ciliary neurons have been described (Panayotatos et al., 1993).

[0120] Pharmacokinetic Determinations—Rats were injected intravenously (i.v.) with rHCNTF (n=1) and RG242 (n=2) at 100 μg/kg and with RG228 (n=1) at 200 μg/kg. Rats were also injected subcutaneously (s.c.) with rHCNTF (n=2), RG242 (n=2) and RG228 (n=1) at 200 μg/kg. Blood specimens were collected prior to dosing and at various times after dosing and were processed to obtain plasma. The plasma specimens were analyzed using the rHCNTF ELISA method for rodent plasma (D. B. Lakings, et al. DSER 93/DMAP/006, “Dose Proportionality and Absolute Bioavailability of rHCNTF in the Rat Following Subcutaneous Administration at Eight Dose Levels” (Phoenix International Project No. 920847) Nov. 10, 1993). The plasma concentrations were evaluated using non compartment techniques. A standard curve for each compound was included on each assay plate and was used to calculate the amount of that compound present in the specimens analyzed on the plate. The sensitivity of the assay varied among compounds by less than twofold.

[0121] Efficacy and Toxicity Determinations In Vivo—Male Sprague-Dawley rats weighing ˜220 g were anesthetized before surgery. The right sciatic nerve was transected at the level of the knee and a 5 mm segment of nerve was removed. Sham surgeries were performed on the left side of each animal. Starting the morning after surgery, rats were weighed and administered vehicle (either PBS or lactate/phosphate/mannitol, pH 4.5) or the rHCNTF compound to be tested, dissolved in the same vehicle at doses ranging from 0.01-1.0 mg/kg, s.c. Rats were weighed and injected daily for 1 week, at which time they were sacrificed and the soleus muscles dissected and weighed. The ratio of the right (denervated) to left (sham) soleus wet weights for each animal was calculated to assess the degree of atrophy caused by denervation and the prevention thereof by treatment with each compound. For assessment of toxicity, the body weights were calculated as a percent of the weight gain of vehicle-treated rats. Both vehicle solutions produced similar results in atrophy and body weight gain.

[0122] Results

[0123] Biological Activity In Vitro—To characterize the activity of rHCNTF in vitro, we measured its effect on mediating the survival of primary dissociated E8 chick ciliary neurons. Neuronal survival in response to increasing concentrations of various human CNTF variants is shown in FIGS. 6, 7 and 8. The variants RG228 (FIG. 7) and RG297 (FIG. 8) that carry the 63QR substitution show 4-5 times greater potency than rHCNTF but the variant RG242 showed a 10-fold weaker potency than rHCNTF, despite the fact that it carries the 63QR substitution. Thus, introduction of various amino acid side chains at various positions of the CNTF sequence has very different effects on the survival of primary neurons in vitro that vary from great loss to strong gain of activity relative to rHCNTF.

[0124] Pharmacokinetics—Before attempting to correlate the in vitro biological potency of a set of compounds to their pharmacological efficacy in vivo, it is useful to determine their absolute bioavailability in the same animal model. In the experiments described below, the disposition kinetics after i.v. administration and the absolute bioavailability after s.c. administration of RG228 and RG242 were determined and compared to those of rHCNTF.

[0125] The average plasma concentration time profiles in the rat after IV administration of rHCNTF, RG228 and RG242 are shown in FIG. 9, normalized to 100 μg/kg dose for all three compounds. The average pharmacokinetic parameters are summarized in Table 1.

[0126] After i.v. administration to rats, RG242 had a distribution phase α somewhat faster than that of rHCNTF and RG228. The disposition phase β for RG242 and RG228 was faster than that of rHCNTF. Thus, RG242 appeared to be distributed into the body and cleared from systemic circulation somewhat more rapidly than rHCNTF, whereas RG228 appeared to be distributed into the body as fast as rHCNTF and cleared from systemic circulation somewhat faster. The area under the concentration time curve (AUC) for RG242 was comparable to that of rHCNTF, indicating that the total body clearance (CI_(T)) was about the same for the two compounds. A twice larger area was observed with RG228. However, the apparent volume of distribution (V_(area)), which is a function of both β and AUC, was approximately twofold smaller for both RG228 and RG242 relative to rHCNTF, suggesting that these variants are distributed less widely. The limited number of animals used in these evaluations did not allow the quantitative distinction of these values. However, these results clearly indicate that the distribution and disposition kinetics of RG228 and RG242 after i.v. administration are not substantially different from those of rHCNTF.

[0127] After s.c. administration, RG228 and RG242 had a 2-3 fold longer absorption phase (Ka) relative to rHCNTF (FIG. 10 and Table 2). The disposition phase of RG242 was also somewhat longer. The longer apparent terminal disposition phase of RG242 after s.c. dosing compared to i.v. administration may be attributed to the incomplete characterization of the terminal phase after the i.v. injection. Overall, the absolute bioavailability of RG228 (13.7%) and RG242 (10.9%) were comparable to that of rHCNTF (6.0%), in view of the fact that in two previous independent studies, the absolute bioavailability of rHCNTF was found to be 14.2% (n=18) and 7.5% (n=8) (D. B. Lakings, et al., DSER 93/DMAP/006, “Dose Proportionality and Absolute Bioavailability of rHCNTF in the Rat Following Subcutaneous Administration at Eight Dose Levels” (Phoenix International Project No. 920847) Nov. 10, 1993; D. B. Lakings, et al., Dose Proportionality and Absolute Bioavailability of rHCNTF Administered Subcutaneously to Rats. AAPS Ninth Annual Meeting, San Diego, Calif., November, 1994). Therefore, the bioavailabilities of rHCNTF, RG228 and RG242 are not significantly different within experimental error.

[0128] Efficacy and Toxicity In Vivo—In control experiments, denervation of the soleus muscle resulted in a loss of 40% of muscle wet weight by 7 days. This value is very accurate and reproducible, since it varies by only 3% among independent experiments. Daily administration of rHCNTF resulted in a dose-dependent rescue of muscle wet weight at an ED₅₀=0.12 mg/kg and a maximal effect at 0.3 mg/kg (FIG. 11). At the same time, even though animals continued to gain weight during the course of these experiments, they clearly did not gain as much as their vehicle-treated counterparts (p<0.01; FIG. 12), especially at the maximally efficacious doses.

[0129] In the course of several experiments conducted in parallel with rHCNTF, it was determined that the 63QR substitution resulted in a 2-fold increase in potency in vivo (FIG. 11) but, also, a concomitant 2 fold increase in toxicity (FIG. 12). In contrast, RG297, which carries the additional C17A and ΔC13 modifications, shows a 2.6 fold greater potency but the same toxicity relative to rHCNTF. Finally, RG242 produced a 2.8 fold increased potency and an 2.4 fold decreased toxicity relative to rHCNTF. These results are summarized in Table 3.

[0130] The relative therapeutic index (T.I.) for each of these compounds was calculated as the ratio of the TD₂₅ and ED₅₀ values, normalized to that of rHCNTF. While the T.I. of RG228 is equal to that of rHCNTF, the T.I. of RG297 and RG242 is 2.5 and 6.8 fold superior to that of rHCNTF, respectively.

[0131] Therefore, RG297 and RG242 have superior pharmacological properties than rHCNTF. This is of great relevance to the clinical situation where decreased body weight is observed upon rHCNTF treatment in humans.

[0132] One skilled in the art will recognize that other alterations in the amino acid sequence of CNTF can result in a biologically active molecule which may have enhanced properties. For example, applicant has prepared a 17CS mutant which has a serine residue in place of the cysteine residue at position 17 and is biologically active. Applicant has also prepared a biologically active quadruple mutant, 17CA,ΔC13,63QR,64WA. Further CNTF mutants, all of which retain biological activity, are set forth in Table 4. TABLE 1 Average Pharmacokinetic Parameters for rHCNTF, RG228 and RG242 after Intravenous Administration to Rats at 100 μg/kg. Pharmacokinetic Compound Parameter rHCNTF RG242 RG228* n 1 2 1 C₀ (ng/ml) 726 2,175 NC AUC_(0−∞)(ng · min/ml) 20,230 22,890 55,800 α (min⁻¹) 0.0492 0.0856 0.041 t_(1/2α) (min) 14 8 17 β (min⁻¹) 0.0106 0.0200 0.0176 t_(1/2β) (min) 65 35 39 V_(area) (ml/kg) 470 220 204 Cl_(T) (ml/min/kg) 4.9 4.4 3.6

[0133] TABLE 2 Average Pharmacokinetic Parameters for rHCNTF, RG228 and RG242 After Subcutaneous Administration to Rats at 200 μg/kg Pharmacokinetic Compound Parameter rHCNTF RG242 RG228 n 2 2 1 C_(max) (ng/ml) 18 32 50 T_(max) (min) 30-45 30-45 60 AUC_(0−∞)(ng · min/ml) 2,425 4,980 7,620 Absolute 6.0 10.9 13.7 Bioavailability k_(e) (min⁻¹) 0.0133 0.0083 NC t_(1/2ke) (min) 52 82 NC k_(a) (min⁻¹) 0.0401 0.0180 0.0102 t_(1/2ka) (min) 17 39 68

[0134] TABLE 3 Efficacy, Toxicity and Therapeutic Index of rHCNTF and Derivatives ED₅₀ TD₂₅ Therapeutic Index Relative Therapeutic Compound (mg/kg) (mg/kg) (TD₂₅/ED₅₀) Index rHCNTF 0.12 0.087 0.72 1.0 RG228 0.065 0.047 0.72 1.0 RG297 0.045 0.080 1.78 2.5 RG242 0.043 0.21 4.88 6.8

[0135] TABLE 4 Biological activity of rHCNTF variants on E8 chick ciliary neurons. Potency units (1/EC₅₀) are shown relative to human CNTF which is assigned a value of 100. One potency unit is defined as the reciprocal ligand concentration showing the same biological activity as 1 ng/ml rHCNTF. CNTF POTENCY rat 500.0 human 100.0 17CS 100.0 63QA 87.0 63QN 100.0 63QH 2.5 63QE <1 63QK 1.1 63QR 400.0 64WA 2.0 63QR64WA 9.0 63QR64WF 250.0 63QR64WH 25.0 63QR64WQ 10.0

[0136]

1 21 200 amino acids amino acid single unknown protein 1 Met Ala Phe Thr Glu His Ser Pro Leu Thr Pro His Arg Arg Asp Leu 1 5 10 15 Cys Ser Arg Ser Ile Trp Leu Ala Arg Lys Ile Arg Ser Asp Leu Thr 20 25 30 Ala Leu Thr Glu Ser Tyr Val Lys His Gln Gly Leu Asn Lys Asn Ile 35 40 45 Asn Leu Asp Ser Ala Asp Gly Met Pro Val Ala Ser Thr Asp Gln Trp 50 55 60 Ser Glu Leu Thr Glu Ala Glu Arg Leu Gln Glu Asn Leu Gln Ala Tyr 65 70 75 80 Arg Thr Phe His Val Leu Leu Ala Arg Leu Leu Glu Asp Gln Gln Val 85 90 95 His Phe Thr Pro Thr Glu Gly Asp Phe His Gln Ala Ile His Thr Leu 100 105 110 Leu Leu Gln Val Ala Ala Phe Ala Tyr Gln Ile Glu Glu Leu Met Ile 115 120 125 Leu Leu Glu Tyr Lys Ile Pro Arg Asn Glu Ala Asp Gly Met Pro Ile 130 135 140 Asn Val Gly Asp Gly Gly Leu Phe Glu Lys Lys Leu Trp Gly Leu Lys 145 150 155 160 Val Leu Gln Glu Leu Ser Gln Trp Thr Val Arg Ser Ile His Asp Leu 165 170 175 Arg Phe Ile Ser Ser His Gln Thr Gly Ile Pro Ala Arg Gly Ser His 180 185 190 Tyr Ile Ala Asn Asn Lys Lys Met 195 200 200 amino acids amino acid single unknown protein 2 Met Ala Phe Ala Glu Gln Thr Pro Leu Thr Leu His Arg Arg Asp Leu 1 5 10 15 Cys Ser Arg Ser Ile Trp Leu Ala Arg Lys Ile Arg Ser Asp Leu Thr 20 25 30 Ala Leu Met Glu Ser Tyr Val Lys His Gln Gly Leu Asn Lys Asn Ile 35 40 45 Asn Leu Asp Ser Val Asp Gly Val Pro Val Ala Ser Thr Asp Arg Trp 50 55 60 Ser Glu Met Thr Glu Ala Glu Arg Leu Gln Glu Asn Leu Gln Ala Tyr 65 70 75 80 Arg Thr Phe Gln Gly Met Leu Thr Lys Leu Leu Glu Asp Gln Arg Val 85 90 95 His Phe Thr Pro Thr Glu Gly Asp Phe His Gln Ala Ile His Thr Leu 100 105 110 Met Leu Gln Val Asp Ala Phe Ala Tyr Gln Leu Glu Glu Leu Met Val 115 120 125 Leu Leu Glu Gln Lys Ile Pro Glu Asn Glu Ala Asp Gly Met Pro Ala 130 135 140 Thr Val Gly Asp Gly Gly Leu Phe Glu Lys Lys Leu Trp Gly Leu Lys 145 150 155 160 Val Leu Gln Glu Leu Ser Gln Trp Thr Val Arg Ser Ile His Asp Leu 165 170 175 Arg Val Ile Ser Ser His Gln Met Gly Ile Ser Ala Leu Glu Ser His 180 185 190 Tyr Gly Ala Lys Asp Lys Gln Met 195 200 199 amino acids amino acid single unknown protein 3 Met Ala Phe Met Glu His Ser Ala Leu Thr Pro His Arg Arg Glu Leu 1 5 10 15 Cys Ser Arg Thr Ile Trp Leu Ala Arg Lys Ile Arg Ser Asp Leu Thr 20 25 30 Ala Leu Thr Glu Ser Tyr Val Lys His Gln Gly Leu Asn Lys Asn Ile 35 40 45 Asn Leu Asp Ser Val Asp Gly Val Pro Met Ala Ser Thr Asp Gln Trp 50 55 60 Ser Glu Leu Thr Glu Ala Glu Arg Leu Gln Glu Asn Leu Gln Ala Tyr 65 70 75 80 Arg Thr Phe His Ile Met Leu Ala Arg Leu Leu Glu Asp Gln Gln Val 85 90 95 His Phe Thr Pro Ala Glu Gly Asp His Phe Gln Ala Ile His Thr Leu 100 105 110 Leu Leu Gln Val Ala Ala Phe Ala Tyr Gln Ile Glu Glu Leu Met Val 115 120 125 Leu Leu Glu Cys Asn Ile Pro Pro Lys Asp Ala Asp Gly Thr Pro Val 130 135 140 Ile Gly Gly Asp Gly Leu Phe Glu Lys Lys Leu Trp Gly Leu Lys Val 145 150 155 160 Leu Gln Glu Leu Ser His Trp Thr Val Arg Ser Ile His Asp Leu Arg 165 170 175 Val Ile Ser Cys His Gln Thr Gly Ile Pro Ala His Gly Ser His Tyr 180 185 190 Ile Ala Asn Asp Lys Glu Met 195 186 amino acids amino acid single unknown protein 4 Met Ala Phe Ala Glu Gln Ser Pro Leu Thr Leu His Arg Arg Asp Leu 1 5 10 15 Cys Ser Arg Ser Ile Trp Leu Ala Arg Lys Ile Arg Ser Asp Leu Thr 20 25 30 Ala Leu Met Glu Ser Tyr Val Lys His Gln Gly Leu Asn Lys Asn Ile 35 40 45 Ser Leu Asp Ser Val Asp Pro Val Ala Ser Thr Asp Arg Trp Ser Glu 50 55 60 Met Thr Glu Ala Glu Arg Leu Gln Glu Asn Leu Gln Ala Tyr Arg Gln 65 70 75 80 Gly Met Leu Thr Arg Leu Leu Glu Asp Gln Arg Val His Phe Thr Pro 85 90 95 Thr Glu Gly Asp Phe His Gln Ala His Thr Leu Thr Gln Val Ser Ala 100 105 110 Phe Ala Tyr Gln Leu Glu Glu Leu Met Ala Leu Leu Glu Gln Lys Val 115 120 125 Asn Glu Ala Asp Gly Met Pro Val Thr Ile Gly Asp Gly Gly Leu Phe 130 135 140 Glu Lys Leu Trp Gly Leu Lys Val Leu Leu Ser Gln Trp Thr Val Arg 145 150 155 160 Ser Ile His Asp Leu Arg Val Ile Ser Ser His His Met Gly Ile Ser 165 170 175 Ala His Ser His Tyr Gly Ala Lys Gln Met 180 185 195 amino acids amino acid single unknown protein 5 Met Ala Ala Ala Asp Thr Pro Ser Ala Thr Leu Arg His His Asp Leu 1 5 10 15 Cys Ser Arg Gly Ile Arg Leu Ala Arg Lys Met Arg Ser Asp Val Thr 20 25 30 Asp Leu Leu Asp Ile Tyr Val Glu Arg Gln Gly Leu Asp Ala Ser Ile 35 40 45 Ser Val Ala Ala Val Asp Gly Val Pro Thr Ala Ala Val Glu Arg Trp 50 55 60 Ala Glu Gln Thr Gly Thr Gln Arg Leu Leu Asp Asn Leu Ala Ala Tyr 65 70 75 80 Arg Ala Phe Arg Thr Leu Leu Ala Gln Met Leu Glu Glu Gln Arg Glu 85 90 95 Leu Leu Gly Asp Thr Asp Ala Glu Leu Gly Pro Ala Leu Ala Ala Met 100 105 110 Leu Leu Gln Val Ser Ala Phe Val Tyr His Leu Glu Glu Leu Leu Glu 115 120 125 Leu Glu Ser Arg Gly Ala Pro Ala Glu Glu Gly Ser Glu Pro Pro Ala 130 135 140 Pro Pro Arg Leu Ser Leu Phe Glu Gln Lys Leu Arg Gly Leu Arg Val 145 150 155 160 Leu Arg Glu Leu Ala Gln Trp Ala Val Arg Ser Val Arg Asp Leu Arg 165 170 175 Gln Leu Ser Lys His Gly Pro Gly Ser Gly Ala Ala Leu Gly Leu Pro 180 185 190 Glu Ser Gln 195 200 amino acids amino acid single unknown protein 6 Met Ala Phe Thr Glu His Ser Pro Leu Thr Pro His Arg Arg Asp Leu 1 5 10 15 Cys Ser Arg Ser Ile Trp Leu Ala Arg Lys Ile Arg Ser Asp Leu Thr 20 25 30 Ala Leu Thr Glu Ser Tyr Val Lys His Gln Gly Leu Asn Lys Asn Ile 35 40 45 Asn Leu Asp Ser Val Asp Gly Val Pro Val Ala Ser Thr Asp Arg Trp 50 55 60 Ser Glu Met Thr Glu Ala Glu Arg Leu Gln Glu Asn Leu Gln Ala Tyr 65 70 75 80 Arg Thr Phe Gln Gly Met Leu Thr Lys Leu Leu Glu Asp Gln Arg Val 85 90 95 His Phe Thr Pro Thr Glu Gly Asp Phe His Gln Ala Ile His Thr Leu 100 105 110 Met Leu Gln Val Ser Ala Phe Ala Tyr Gln Leu Glu Glu Leu Met Val 115 120 125 Leu Leu Glu Gln Lys Ile Pro Glu Asn Glu Ala Asp Gly Met Pro Ala 130 135 140 Thr Val Gly Asp Gly Gly Leu Phe Glu Lys Lys Leu Trp Gly Leu Lys 145 150 155 160 Val Leu Gln Glu Leu Ser Gln Trp Thr Val Arg Ser Ile His Asp Leu 165 170 175 Arg Val Ile Ser Ser His Gln Met Gly Ile Ser Ala Leu Glu Ser His 180 185 190 Tyr Gly Ala Lys Asp Lys Gln Met 195 200 200 amino acids amino acid single unknown protein 7 Met Ala Phe Ala Glu Gln Thr Pro Leu Thr Leu His Arg Arg Asp Leu 1 5 10 15 Cys Ser Arg Ser Ile Trp Leu Ala Arg Lys Ile Arg Ser Asp Leu Thr 20 25 30 Ala Leu Met Glu Ser Tyr Val Lys His Gln Gly Leu Asn Lys Asn Ile 35 40 45 Asn Leu Asp Ser Ala Asp Gly Met Pro Val Ala Ser Thr Asp Gln Trp 50 55 60 Ser Glu Leu Thr Glu Ala Glu Arg Leu Gln Glu Asn Leu Gln Ala Tyr 65 70 75 80 Arg Thr Phe His Val Leu Leu Ala Arg Leu Leu Glu Asp Gln Gln Val 85 90 95 His Phe Thr Pro Thr Glu Gly Asp Phe His Gln Ala Ile His Thr Leu 100 105 110 Leu Leu Gln Val Ala Ala Phe Ala Tyr Gln Ile Glu Glu Leu Met Ile 115 120 125 Leu Leu Glu Tyr Lys Ile Pro Arg Asn Glu Ala Asp Gly Met Pro Ile 130 135 140 Asn Val Gly Asp Gly Gly Leu Phe Glu Lys Lys Leu Trp Gly Leu Lys 145 150 155 160 Val Leu Gln Glu Leu Ser Gln Trp Thr Val Arg Ser Ile His Asp Leu 165 170 175 Arg Phe Ile Ser Ser His Gln Thr Gly Ile Pro Ala Arg Gly Ser His 180 185 190 Tyr Ile Ala Asn Asn Lys Lys Met 195 200 200 amino acids amino acid single unknown protein 8 Met Ala Phe Thr Glu His Ser Pro Leu Thr Pro His Arg Arg Asp Leu 1 5 10 15 Cys Ser Arg Ser Ile Trp Leu Ala Arg Lys Ile Arg Ser Asp Leu Thr 20 25 30 Ala Leu Thr Glu Ser Tyr Val Lys His Gln Gly Leu Asn Lys Asn Ile 35 40 45 Asn Leu Asp Ser Ala Asp Gly Met Pro Val Ala Ser Thr Asp Gln Trp 50 55 60 Ser Glu Leu Thr Glu Ala Glu Arg Leu Gln Glu Asn Leu Gln Ala Tyr 65 70 75 80 Arg Thr Phe His Val Leu Leu Ala Arg Leu Leu Glu Asp Gln Gln Val 85 90 95 His Phe Thr Pro Thr Glu Gly Asp Phe His Gln Ala Ile His Thr Leu 100 105 110 Leu Leu Gln Val Ala Ala Phe Ala Tyr Gln Ile Glu Glu Leu Met Ile 115 120 125 Leu Leu Glu Tyr Lys Ile Pro Arg Asn Glu Ala Asp Gly Met Pro Ile 130 135 140 Asn Val Gly Asp Gly Gly Leu Phe Glu Lys Lys Leu Trp Gly Leu Lys 145 150 155 160 Val Leu Gln Glu Leu Ser Gln Trp Thr Val Arg Ser Ile His Asp Leu 165 170 175 Arg Val Ile Ser Ser His Gln Met Gly Ile Ser Ala Leu Glu Ser His 180 185 190 Tyr Gly Ala Lys Asp Lys Gln Met 195 200 200 amino acids amino acid single unknown protein 9 Met Ala Phe Ala Glu Gln Thr Pro Leu Thr Leu His Arg Arg Asp Leu 1 5 10 15 Cys Ser Arg Ser Ile Trp Leu Ala Arg Lys Ile Arg Ser Asp Leu Thr 20 25 30 Ala Leu Met Glu Ser Tyr Val Lys His Gln Gly Leu Asn Lys Asn Ile 35 40 45 Asn Leu Asp Ser Val Asp Gly Val Pro Val Ala Ser Thr Asp Arg Trp 50 55 60 Ser Glu Met Thr Glu Ala Glu Arg Leu Gln Glu Asn Leu Gln Ala Tyr 65 70 75 80 Arg Thr Phe Gln Gly Met Leu Thr Lys Leu Leu Glu Asp Gln Arg Val 85 90 95 His Phe Thr Pro Thr Glu Gly Asp Phe His Gln Ala Ile His Thr Leu 100 105 110 Met Leu Gln Val Ser Ala Phe Ala Tyr Gln Leu Glu Glu Leu Met Val 115 120 125 Leu Leu Glu Gln Lys Ile Pro Glu Asn Glu Ala Asp Gly Met Pro Ala 130 135 140 Thr Val Gly Asp Gly Gly Leu Phe Glu Lys Lys Leu Trp Gly Leu Lys 145 150 155 160 Val Leu Gln Glu Leu Ser Gln Trp Thr Val Arg Ser Ile His Asp Leu 165 170 175 Arg Phe Ile Ser Ser His Gln Thr Gly Ile Pro Ala Arg Gly Ser His 180 185 190 Tyr Ile Ala Asn Asn Lys Lys Met 195 200 200 amino acids amino acid single unknown protein 10 Met Ala Phe Thr Glu His Ser Pro Leu Thr Pro His Arg Arg Asp Leu 1 5 10 15 Cys Ser Arg Ser Ile Trp Leu Ala Arg Lys Ile Arg Ser Asp Leu Thr 20 25 30 Ala Leu Thr Glu Ser Tyr Val Lys His Gln Gly Leu Asn Lys Asn Ile 35 40 45 Asn Leu Asp Ser Ala Asp Gly Met Pro Val Ala Ser Thr Asp Gln Trp 50 55 60 Ser Glu Leu Thr Glu Ala Glu Arg Leu Gln Glu Asn Leu Gln Ala Tyr 65 70 75 80 Arg Thr Phe Gln Gly Met Leu Thr Lys Leu Leu Glu Asp Gln Arg Val 85 90 95 His Phe Thr Pro Thr Glu Gly Asp Phe His Gln Ala Ile His Thr Leu 100 105 110 Met Leu Gln Val Ser Ala Phe Ala Tyr Gln Leu Glu Glu Leu Met Val 115 120 125 Leu Leu Glu Gln Lys Ile Pro Glu Asn Glu Ala Asp Gly Met Pro Ala 130 135 140 Thr Val Gly Asp Gly Gly Leu Phe Glu Lys Lys Leu Trp Gly Leu Lys 145 150 155 160 Val Leu Gln Glu Leu Ser Gln Trp Thr Val Arg Ser Ile His Asp Leu 165 170 175 Arg Phe Ile Ser Ser His Gln Thr Gly Ile Pro Ala Arg Gly Ser His 180 185 190 Tyr Ile Ala Asn Asn Lys Lys Met 195 200 200 amino acids amino acid single unknown protein 11 Met Ala Phe Thr Glu His Ser Pro Leu Thr Pro His Arg Arg Asp Leu 1 5 10 15 Cys Ser Arg Ser Ile Trp Leu Ala Arg Lys Ile Arg Ser Asp Leu Thr 20 25 30 Ala Leu Met Glu Ser Tyr Val Lys His Gln Gly Leu Asn Lys Asn Ile 35 40 45 Asn Leu Asp Ser Val Asp Gly Val Pro Val Ala Ser Thr Asp Arg Trp 50 55 60 Ser Glu Met Thr Glu Ala Glu Arg Leu Gln Glu Asn Leu Gln Ala Tyr 65 70 75 80 Arg Thr Phe His Val Leu Leu Ala Arg Leu Leu Glu Asp Gln Gln Val 85 90 95 His Phe Thr Pro Thr Glu Gly Asp Phe His Gln Ala Ile His Thr Leu 100 105 110 Leu Leu Gln Val Ala Ala Phe Ala Tyr Gln Ile Glu Glu Leu Met Ile 115 120 125 Leu Leu Glu Tyr Lys Ile Pro Arg Asn Glu Ala Asp Gly Met Pro Ile 130 135 140 Asn Val Gly Asp Gly Gly Leu Phe Glu Lys Lys Leu Trp Gly Leu Lys 145 150 155 160 Val Leu Gln Glu Leu Ser Gln Trp Thr Val Arg Ser Ile His Asp Leu 165 170 175 Arg Phe Ile Ser Ser His Gln Thr Gly Ile Pro Ala Arg Gly Ser His 180 185 190 Tyr Ile Ala Asn Asn Lys Lys Met 195 200 200 amino acids amino acid single unknown protein 12 Met Ala Phe Thr Glu His Ser Pro Leu Thr Pro His Arg Arg Asp Leu 1 5 10 15 Cys Ser Arg Ser Ile Trp Leu Ala Arg Lys Ile Arg Ser Asp Leu Thr 20 25 30 Ala Leu Thr Glu Ser Tyr Val Lys His Gln Gly Leu Asn Lys Asn Ile 35 40 45 Asn Leu Asp Ser Val Asp Gly Val Pro Val Ala Ser Thr Asp Arg Trp 50 55 60 Ser Glu Met Thr Glu Ala Glu Arg Leu Gln Glu Asn Leu Gln Ala Tyr 65 70 75 80 Arg Thr Phe His Val Leu Leu Ala Arg Leu Leu Glu Asp Gln Gln Val 85 90 95 His Phe Thr Pro Thr Glu Gly Asp Phe His Gln Ala Ile His Thr Leu 100 105 110 Leu Leu Gln Val Ala Ala Phe Ala Tyr Gln Ile Glu Glu Leu Met Ile 115 120 125 Leu Leu Glu Tyr Lys Ile Pro Arg Asn Glu Ala Asp Gly Met Pro Ile 130 135 140 Asn Val Gly Asp Gly Gly Leu Phe Glu Lys Lys Leu Trp Gly Leu Lys 145 150 155 160 Val Leu Gln Glu Leu Ser Gln Trp Thr Val Arg Ser Ile His Asp Leu 165 170 175 Arg Phe Ile Ser Ser His Gln Thr Gly Ile Pro Ala Arg Gly Ser His 180 185 190 Tyr Ile Ala Asn Asn Lys Lys Met 195 200 200 amino acids amino acid single unknown protein 13 Met Ala Phe Thr Glu His Ser Pro Leu Thr Pro His Arg Arg Asp Leu 1 5 10 15 Cys Ser Arg Ser Ile Trp Leu Ala Arg Lys Ile Arg Ser Asp Leu Thr 20 25 30 Ala Leu Thr Glu Ser Tyr Val Lys His Gln Gly Leu Asn Lys Asn Ile 35 40 45 Asn Leu Asp Ser Val Asp Gly Met Pro Val Ala Ser Thr Asp Gln Trp 50 55 60 Ser Glu Met Thr Glu Ala Glu Arg Leu Gln Glu Asn Leu Gln Ala Tyr 65 70 75 80 Arg Thr Phe His Val Leu Leu Ala Arg Leu Leu Glu Asp Gln Gln Val 85 90 95 His Phe Thr Pro Thr Glu Gly Asp Phe His Gln Ala Ile His Thr Leu 100 105 110 Leu Leu Gln Val Ala Ala Phe Ala Tyr Gln Ile Glu Glu Leu Met Ile 115 120 125 Leu Leu Glu Tyr Lys Ile Pro Arg Asn Glu Ala Asp Gly Met Pro Ile 130 135 140 Asn Val Gly Asp Gly Gly Leu Phe Glu Lys Lys Leu Trp Gly Leu Lys 145 150 155 160 Val Leu Gln Glu Leu Ser Gln Trp Thr Val Arg Ser Ile His Asp Leu 165 170 175 Arg Phe Ile Ser Ser His Gln Thr Gly Ile Pro Ala Arg Gly Ser His 180 185 190 Tyr Ile Ala Asn Asn Lys Lys Met 195 200 200 amino acids amino acid single unknown protein 14 Met Ala Phe Thr Glu His Ser Pro Leu Thr Pro His Arg Arg Asp Leu 1 5 10 15 Cys Ser Arg Ser Ile Trp Leu Ala Arg Lys Ile Arg Ser Asp Leu Thr 20 25 30 Ala Leu Thr Glu Ser Tyr Val Lys His Gln Gly Leu Asn Lys Asn Ile 35 40 45 Asn Leu Asp Ser Val Asp Gly Val Pro Val Ala Ser Thr Asp Gln Trp 50 55 60 Ser Glu Leu Thr Glu Ala Glu Arg Leu Gln Glu Asn Leu Gln Ala Tyr 65 70 75 80 Arg Thr Phe His Val Leu Leu Ala Arg Leu Leu Glu Asp Gln Gln Val 85 90 95 His Phe Thr Pro Thr Glu Gly Asp Phe His Gln Ala Ile His Thr Leu 100 105 110 Leu Leu Gln Val Ala Ala Phe Ala Tyr Gln Ile Glu Glu Leu Met Ile 115 120 125 Leu Leu Glu Tyr Lys Ile Pro Arg Asn Glu Ala Asp Gly Met Pro Ile 130 135 140 Asn Val Gly Asp Gly Gly Leu Phe Glu Lys Lys Leu Trp Gly Leu Lys 145 150 155 160 Val Leu Gln Glu Leu Ser Gln Trp Thr Val Arg Ser Ile His Asp Leu 165 170 175 Arg Phe Ile Ser Ser His Gln Thr Gly Ile Pro Ala Arg Gly Ser His 180 185 190 Tyr Ile Ala Asn Asn Lys Lys Met 195 200 200 amino acids amino acid single unknown protein 15 Met Ala Phe Thr Glu His Ser Pro Leu Thr Pro His Arg Arg Asp Leu 1 5 10 15 Cys Ser Arg Ser Ile Trp Leu Ala Arg Lys Ile Arg Ser Asp Leu Thr 20 25 30 Ala Leu Thr Glu Ser Tyr Val Lys His Gln Gly Leu Asn Lys Asn Ile 35 40 45 Asn Leu Asp Ser Ala Asp Gly Met Pro Val Ala Ser Thr Asp Arg Trp 50 55 60 Ser Glu Leu Thr Glu Ala Glu Arg Leu Gln Glu Asn Leu Gln Ala Tyr 65 70 75 80 Arg Thr Phe His Val Leu Leu Ala Arg Leu Leu Glu Asp Gln Gln Val 85 90 95 His Phe Thr Pro Thr Glu Gly Asp Phe His Gln Ala Ile His Thr Leu 100 105 110 Leu Leu Gln Val Ala Ala Phe Ala Tyr Gln Ile Glu Glu Leu Met Ile 115 120 125 Leu Leu Glu Tyr Lys Ile Pro Arg Asn Glu Ala Asp Gly Met Pro Ile 130 135 140 Asn Val Gly Asp Gly Gly Leu Phe Glu Lys Lys Leu Trp Gly Leu Lys 145 150 155 160 Val Leu Gln Glu Leu Ser Gln Trp Thr Val Arg Ser Ile His Asp Leu 165 170 175 Arg Phe Ile Ser Ser His Gln Thr Gly Ile Pro Ala Arg Gly Ser His 180 185 190 Tyr Ile Ala Asn Asn Lys Lys Met 195 200 21 base pairs nucleic acid single linear DNA (genomic) 16 ACGGTAAGCT TGGAGGTTCT C 21 48 base pairs nucleic acid single linear DNA (genomic) 17 TCTATCTGGC TAGCAAGGAA GATTCGTTCA GACCTGACTG CTCTTACG 48 69 base pairs nucleic acid single linear DNA (genomic) 18 AAGGTACGAT AAGCTTGGAG GTTCTCTTGG AGTCGCTCTG CCTCAGTCAG CTCACTCCAA 60 CGATCAGTG 69 21 base pairs nucleic acid single unknown DNA (genomic) 19 TCTATCTGGC TAGCAAGGAA G 21 782 base pairs nucleic acid single linear DNA Human CNTF 126...725 20 GTGCACAATC CCATTAGTAG AGAATGCCAG TGGGTTTAGT CTTTGAGAGT CACATCTCTT 60 ATTTGGACCA GTATAGACAG AAGTAAACCC AGCTGACTTG TTTCCTGGGA CAGTTGAGTT 120 AAGGG ATG GCT TTC ACA GAG CAT TCA CCG CTG ACC CCT CAC CGT CGG GAC 170 Met Ala Phe Thr Glu His Ser Pro Leu Thr Pro His Arg Arg Asp 1 5 10 15 CTC TGT AGC CGC TCT ATC TGG CTA GCA AGG AAG ATT CGT TCA GAC CTG 218 Leu Cys Ser Arg Ser Ile Trp Leu Ala Arg Lys Ile Arg Ser Asp Leu 20 25 30 ACT GCT CTT ACG GAA TCC TAT GTG AAG CAT CAG GGC CTG AAC AAG AAC 266 Thr Ala Leu Thr Glu Ser Tyr Val Lys His Gln Gly Leu Asn Lys Asn 35 40 45 ATC AAC CTG GAC TCT GCG GAT GGG ATG CCA GTG GCA AGC ACT GAT CAG 314 Ile Asn Leu Asp Ser Ala Asp Gly Met Pro Val Ala Ser Thr Asp Gln 50 55 60 TGG AGT GAG CTG ACC GAG GCA GAG CGA CTC CAA GAG AAC CTT CAA GCT 362 Trp Ser Glu Leu Thr Glu Ala Glu Arg Leu Gln Glu Asn Leu Gln Ala 65 70 75 TAT CGT ACC TTC CAT GTT TTG TTG GCC AGG CTC TTA GAA GAC CAG CAG 410 Tyr Arg Thr Phe His Val Leu Leu Ala Arg Leu Leu Glu Asp Gln Gln 80 85 90 95 GTG CAT TTT ACC CCA ACC GAA GGT GAC TTC CAT CAA GCT ATA CAT ACC 458 Val His Phe Thr Pro Thr Glu Gly Asp Phe His Gln Ala Ile His Thr 100 105 110 CTT CTT CTC CAA GTC GCT GCC TTT GCA TAC CAG ATA GAG GAG TTA ATG 506 Leu Leu Leu Gln Val Ala Ala Phe Ala Tyr Gln Ile Glu Glu Leu Met 115 120 125 ATA CTC CTG GAA TAC AAG ATC CCC CGC AAT GAG GCT GAT GGG ATG CCT 554 Ile Leu Leu Glu Tyr Lys Ile Pro Arg Asn Glu Ala Asp Gly Met Pro 130 135 140 ATT AAT GTT GGA GAT GGT GGT CTC TTT GAG AAG AAG CTG TGG GGC CTA 602 Ile Asn Val Gly Asp Gly Gly Leu Phe Glu Lys Lys Leu Trp Gly Leu 145 150 155 AAG GTG CTG CAG GAG CTT TCA CAG TGG ACA GTA AGG TCC ATC CAT GAC 650 Lys Val Leu Gln Glu Leu Ser Gln Trp Thr Val Arg Ser Ile His Asp 160 165 170 175 CTT CGT TTC ATT TCT TCT CAT CAG ACT GGG ATC CCA GCA CGT GGG AGC 698 Leu Arg Phe Ile Ser Ser His Gln Thr Gly Ile Pro Ala Arg Gly Ser 180 185 190 CAT TAT ATT GCT AAC AAC AAG AAA ATG TAGCAGTTAG TCCCTTCTCT CTTCCTT 752 His Tyr Ile Ala Asn Asn Lys Lys Met 195 200 ACTTTCTCTT CTAATGGAAT ATGCGTAGTT 782 200 amino acids amino acid single linear protein internal 21 Met Ala Phe Thr Glu His Ser Pro Leu Thr Pro His Arg Arg Asp Leu 1 5 10 15 Cys Ser Arg Ser Ile Trp Leu Ala Arg Lys Ile Arg Ser Asp Leu Thr 20 25 30 Ala Leu Thr Glu Ser Tyr Val Lys His Gln Gly Leu Asn Lys Asn Ile 35 40 45 Asn Leu Asp Ser Ala Asp Gly Met Pro Val Ala Ser Thr Asp Gln Trp 50 55 60 Ser Glu Leu Thr Glu Ala Glu Arg Leu Gln Glu Asn Leu Gln Ala Tyr 65 70 75 80 Arg Thr Phe His Val Leu Leu Ala Arg Leu Leu Glu Asp Gln Gln Val 85 90 95 His Phe Thr Pro Thr Glu Gly Asp Phe His Gln Ala Ile His Thr Leu 100 105 110 Leu Leu Gln Val Ala Ala Phe Ala Tyr Gln Ile Glu Glu Leu Met Ile 115 120 125 Leu Leu Glu Tyr Lys Ile Pro Arg Asn Glu Ala Asp Gly Met Pro Ile 130 135 140 Asn Val Gly Asp Gly Gly Leu Phe Glu Lys Lys Leu Trp Gly Leu Lys 145 150 155 160 Val Leu Gln Glu Leu Ser Gln Trp Thr Val Arg Ser Ile His Asp Leu 165 170 175 Arg Phe Ile Ser Ser His Gln Thr Gly Ile Pro Ala Arg Gly Ser His 180 185 190 Tyr Ile Ala Asn Asn Lys Lys Met 195 200 

I claim:
 1. Human ciliary neurotrophic factor having the modification Gln63→Arg.
 2. Modified ciliary neurotrophic factor according to claim 1, further having the modification Trp64→Ala.
 3. Modified ciliary neurotrophic factor according to claim 1, further having the modification Cys17→Ala and a deletion of the terminal 13 amino acid residues.
 4. Modified ciliary neurotrophic factor according to claim 1, further having a deletion of the terminal 13 amino acid residues.
 5. The modified ciliary neurotrophic factor of claim 2, designated RG
 242. 6. The modified ciliary neurotrophic factor of claim 3, designated RG
 297. 7. The modified ciliary neurotrophic factor of claim 4, designated RG
 290. 8. An isolated and purified nucleic acid molecule encoding the modified human CNTF of claim 1, 2, 3 or
 4. 9. A recombinant DNA molecule of claim 8, operatively linked to an expression control sequence.
 10. A host cell transformed with the recombinant DNA molecule of claim
 8. 11. A method for producing a modified CNTF molecule comprising: (a) growing a recombinant host cell containing the DNA molecule of claim 8, so that the DNA molecule is expressed by the host cell to produce the modified CNTF molecule and (b) isolating the expressed, modified CNTF molecule.
 12. The method according to claim 11, wherein said host cell is a eukaryotic cell.
 13. The method according to claim 11, wherein said host cell is a prokaryotic cell.
 14. A pharmaceutical composition comprising a therapeutically effective amount of a substantially pure modified ciliary neurotrophic factor according to claim 1, 2, 3 or 4 in a pharmaceutically suitable carrier.
 15. A method of treating a disease or disorder of the nervous system comprising administering to a patient an effective amount of the modified ciliary neurotrophic factor of claim 1, 2, 3 or
 4. 16. The method according to claim 15, wherein said disease or disorder is a degenerative disease.
 17. The method according to claim 15, wherein said disease or disorder involves the spinal cord, motor neurons, cholinergic neurons or cells of the hippocampus.
 18. The method according to claim 15, in which the disease or disorder of the nervous system comprises damage to the nervous system caused by an event selected from the group consisting of trauma, surgery, infarction, infection, malignancy and exposure to a toxic agent.
 19. The method according to claim 15, wherein said disease or disorder involves muscle atrophy.
 20. A method of identifying a human protein with enhanced biological activity and/or binding affinity comprising: (a) determining the SDS-PAGE electrophoretic mobility of a wild-type human protein; (b) introducing an amino acid substitution in said wild-type human protein to produce a substituted protein; (c) comparing the electrophoretic mobility of the substituted protein to the electrophoretic mobility of the wild-type protein; (d) identifying a substituted protein with altered electrophoretic mobility as compared to the electrophoretic mobility of the wild-type protein; and (e) determining the biological activity and/or binding affinity of the identified substituted protein and thereby identifying a human protein with enhanced biological activity and/or binding affinity.
 21. The method according to claim 20, wherein the amino acid substitution in the wild-type human protein corresponds to an amino acid found in a sequence of a homologous protein of a different animal species. 